Embodiments of the invention pertain to the field of computer graphics generally, and more specifically to the loading of graphical tiles into volatile memory. Users of mobile devices such as smart phones often use their mobile devices to perform navigation functions. Mobile devices are often equipped with global position systems (GPS) that can inform the mobile devices as to their current whereabouts. Some popular navigation applications executable on mobile devices include map applications that can display, to the user, geographical information about the mobile device's current surroundings. For example, a navigation application might use a mobile device's GPS to determine its current coordinates, and then present, to a user, a map of an area of specified dimensions centered around the mobile device's location. Such a map might include markings such as streets and labeled points of interest.
Such a navigation application might be capable of presenting maps of areas found in various places all over the globe. Map data for the entire globe might be divided into rectangular tiles. Each tile may contain map data for a different portion of the globe. The globe is a large environment, though, and mobile devices often have limited memory and limited storage capabilities. It might not be feasible for a state-of-the-art mobile device to store, within its memory, all at once, all of the tiles for the entire globe. Indeed, even if a mobile device were equipped with sufficient memory to store all of the globe's map tiles concurrently, it might not be desirable for the mobile device to occupy its limited memory resources overwhelmingly with map tiles. At any given moment, the mobile device's user typically is interested in viewing just one selected section of the map, which may include just a small fraction of all of the map's tiles. Additionally, a mobile device's user often will want to store and execute multiple different applications, so such applications usually need to share the mobile device's limited memory and storage resources. It is unlikely that a mobile device's user will want his mobile device's memory to be dominated by map tiles to the exclusion of other information that could be stored in that memory.